1. Field of the Invention
Injectors for fuel standing under extremely high pressure have a valve controlling the injection process, as well as a nozzle needle projecting into the combustion chamber of an internal combustion machine. For actuation of the injectors, these as a rule are equipped with solenoid valves with which the shortest actuation times can be realized.
2. Description of the Prior Art
Injectors for internal combustion machines have been disclosed on the basis of the state of the art which can be outfitted with multiway valves. As a rule, solenoid valves are used for actuating injectors with which very short operating times can be realized. Since the injectors in certain injector ranges can be acted upon by pressures up to 1600 bar in order to produce an injection process in connection with extremely highly compressing diesel motors, leakage losses arise on the surfaces upon which relative motions occur through moving parts and on the components which separate highest pressure spaces from such with (viewed in relation to them) lower pressures. Leakage losses arise from injection process to injection process and can, for example, be adjusted by needle diameter and by control valve diameter. Leakage losses of fuel in the combustion chamber of an internal combustion machine can lead to so-called xe2x80x9credieselingxe2x80x9d after switching the machine off it, for example, leakage losses occur on the nozzle needle opening into the combustion chamber. In contrast, leakage losses can just as well occur at the opposite end of the injector, perhaps on the solenoid valve serving as a 2/2 way valve.
With the injector solution of the invention for highest fuel injector pressures, leakage losses at the nozzle needle valve from injection process to injection process can be prevented. The losses arising on the magnet-side end of the injector in the region of the throttle merely represent solenoid valve control amount losses which can be returned to the storage tank again through a return line. If the injector is not subjected to systemic pressure, then a locking spring accommodated on the solenoid valve assures that the casing and the nozzle needle are pressed in the direction of the nozzle needle seat, and this remains shut against the combustion chamber. If the injector in contrast is acted upon with systemic pressure, then the fuel entering through the junction into the nozzle needle control space under high pressure makes it possible for the nozzle needle projecting into the nozzle needle control space to be likewise acted upon with high fuel systemic pressure on its face. Since the diameter on the nozzle needle is dimensioned larger on the control space side end than on the nozzle needle seat, a seating action is produced on the side of the nozzle through the pressurization of the nozzle needle control space at the end of the injector element.
Only when the solenoid valve accommodated in the injector element is subject to flow does a reduction in pressure take place in the nozzle needle control space. This is brought about in that the throttle opening is provided with a greater diameter on the solenoid valve side than the inlet throttle to the nozzle needle control space between the face end of the casing and the opposite end of the nozzle needle drops. The nozzle needle is moved through the high pressure arising now as before at the nozzle end to the control space side face of the casing. The injection process beings. The end of the injection process [tales] takes place through a pressure surge appearing in the axial bore hole of the casing after cessation of subjecting the solenoid valve to current. The pressure wave appearing in the axial bore hole of the casing after closing the solenoid valve is reproduced through this up into the nozzle needle control space and brings about a lightning-like pressing of the nozzle needle on its seat on the combustion chamber side end of the nozzle. This increase in pressure, also known as the xe2x80x9chammer pipe effectxe2x80x9d acts on the side of the nozzle needle facing the nozzle needle control area, whose diameter is greater than the diameter of the nozzle needle at the nozzle needle seat. The nozzle needle closes the nozzle opening lightning-like through the rise in pressure in the casing such that leakage losses in solenoid valve control amount remain restricted.
A further advantage of the solution provided according to the invention is to be seen in the circumstance that only a minimal amount of subassemblies on the injector are required. It basically is a matter of the nozzle, the control valve, the casing and the injector element.